Using a Separate Motor Power Source

The Handy Board's internal battery provides a 9.6 volt power supply for operating DC motors. This is generally adequate for powering motors rated between 6 and 12 volts. 6-volt motors will run somewhat ``hot'' with the internal battery supply; this can be tempered by using software motor control to operate the motors at less than 100% of full power.

If it is desired to run motors at a different voltage than the internal battery can provide, the instructions provided here explain how to modify the Handy Board to accept a secondary battery for powering motors. This separate motor battery can provide any voltage from about 6 volts to 36 volts.

The procedure requires cutting the thick motor power trace, and then plugging in the new motor battery into the motor power header. The diagram below shows where to cut the motor power trace.

Use a sharp razor knife to cut the trace. Make two vertical slices across the trace about 1/8 of an inch apart, and then ``peel off'' the metal trace left in between the two slices. Make sure to remove all the metal so that the trace is indeed severed.

To build the adapter to connect the new motor power battery to the Handy Board, see the diagram below. The connector is a four--pin male header connector; two pins each are used for the positive and negative power terminals.

The external motor battery plugs into the Handy Board at the motor power jack indicated in the first diagram. On the Handy Board itself, the left side of the jack is labeled positive (+) and the right side is labeled negative (-).

Since the motor jack is not physically polarized, it is critical that the external motor battery is not plugged in backward by accident. It is suggested that a visible marking be applied to the board jack and/or the battery plug so that the proper orientation is evident.
For example, typewriter correction fluid can be applied to the connectors to indicate the positive terminals.

(Thanks to Larry Randall for first pointing out this method.)

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Fred Martin / MIT Media Laboratory
Last updated: Sun Apr 14 13:52:12 1996